644752 has 20 divisors (see below), whose sum is σ = 1272240. Its totient is φ = 316448.

The previous prime is 644747. The next prime is 644753. The reversal of 644752 is 257446.

It is a self number, because there is not a number n which added to its sum of digits gives 644752.

It is not an unprimeable number, because it can be changed into a prime (644753) by changing a digit.

644752 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 603 + ... + 1285.

It is an arithmetic number, because the mean of its divisors is an integer number (63612).

2⁶⁴⁴⁷⁵² is an apocalyptic number.

It is an amenable number.

644752 is a deficient number, since it is larger than the sum of its proper divisors (627488).

644752 is a wasteful number, since it uses less digits than its factorization.

644752 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 750 (or 744 counting only the distinct ones).

The product of its digits is 6720, while the sum is 28.

The square root of 644752 is about 802.9645073103. The cubic root of 644752 is about 86.3901509121.

The spelling of 644752 in words is "six hundred forty-four thousand, seven hundred fifty-two".